Don't need to wait for test node deployment now that we're waiting for an exit code with Paramiko
Messenger will now take a topic. Plus, fix up a comment.
Add two new exceptions that inherit from EC2ServiceException
Update messenger calls since message() now takes a topic
Use the new, more-specific exception rather than the old, parent exception
Add/tweak some comments about volume deletion
Only try to upload an AMI to other regions if the tests pass